JP2007212479A - System and method for defect inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and method for defect inspection which can discriminate various shaped scratches from adhered foreign substances, generated on the surface of any processed subject to be inspected, when implementing of grinding or polishing, such as Chemical Mechanical Polishing (CMP) on the processed subject (for example, insulating film on semiconductor substrate) is conducted, in the manufacturing of semiconductor or magnetic head. <P>SOLUTION: The present invention is characterized in that epi-illumination and oblique illumination are applied by using almost the same luminous flux to scratches or foreign substances generated on surface of polished or ground insulating film to discriminate shallow scratches from foreign substances, based on correlation between the times of the epi-illumination and the oblique illumination, such as the intensity ratios of the scattered lights generated from both the shallow scratches and the foreign substances. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a defect inspection apparatus and method for discriminating and inspecting defects such as scratches and particulate foreign matters generated in a flattening process using a polishing or grinding technique used when manufacturing a semiconductor or a magnetic head.

  As conventional techniques for discriminating foreign substances adhering to a semiconductor wafer on which a circuit pattern is formed from circuit patterns and inspecting them, Japanese Patent Application Laid-Open No. 3-102248 (Patent Document 1) and Japanese Patent Application Laid-Open No. 3-102249 (Patent Document 2). )It has been known. That is, in Patent Documents 1 and 2, foreign matter on a semiconductor substrate is emphasized by oblique illumination and detected by the first photoelectric conversion element, and the edge of the circuit pattern that is the background on the semiconductor substrate is reflected by epi-illumination. The foreign matter detection signal is detected by the second photoelectric conversion element with emphasis and the foreign matter detection signal obtained from the first photoelectric conversion element is divided by the detection signal obtained from the second photoelectric conversion element. It is described that the above foreign matter is detected with emphasis on the above.

  Japanese Patent Laid-Open No. 9-304289 (Patent Document 3) is known as a conventional technique for separating and inspecting foreign matter adhering to the surface of a silicon wafer and crystal defects existing on the surface. That is, Patent Document 3 includes a low-angle light receiving system having an elevation angle of 30 ° or less with respect to the surface of the silicon wafer, and a high-angle light receiving system having an elevation angle larger than this, Scattered light obtained by irradiating the surface of the silicon wafer substantially perpendicularly is received by the low-angle light receiving system and the high-angle light receiving system, and a crystal defect is received only by the high-angle light receiving system. In addition, it is described that the light received by the low-angle light-receiving system and the high-angle light-receiving system is discriminated as an attached foreign substance and inspected.

  Japanese Patent Laid-Open No. 11-142127 discloses a conventional technique for distinguishing and inspecting foreign matters and scratches existing on the surface of a semiconductor wafer without misidentifying a minute dot-like recess that does not become an obstacle when creating a circuit pattern. (Patent Document 4) is known. That is, Patent Document 4 condenses and irradiates each of two different wavelengths of illumination light on the same point on the surface of the semiconductor wafer at different low and high incident angles. The scattered light from the light spot is received separately for two wavelengths and photoelectrically converted, and the difference in intensity between the signals, that is, the intensity of the scattered light by the illumination light at a low incident angle is weakened from the point-shaped recess is utilized. Thus, it is described that a foreign substance or a flaw existing on the surface of a semiconductor wafer is inspected separately from a spot-like recess.

Japanese Patent Laid-Open No. 3-102248 Japanese Patent Laid-Open No. 3-102249 JP-A-9-304289 Japanese Patent Laid-Open No. 11-142127

  By the way, as a planarization technique used for an object to be processed (for example, an insulating film) when manufacturing a semiconductor or a magnetic head, a typical one is CMP (Chemical Mechanical Polishing). This CMP is a flattening technique in which free abrasive grains such as silica are dispersed on a polishing pad to polish the surface of a workpiece. Further, as a planarization processing technique, there is a case where a grinding technique is used in which fixed abrasive grains such as diamond are embedded in a polishing pad and grinding is performed in the same manner. In these polishing or grinding techniques, scratches having various shapes, which are polishing or grinding flaws, are generated on the surface of an object to be processed (for example, an insulating film on a semiconductor substrate (wafer)) after polishing or grinding. is there. As described above, in the manufacture of semiconductors and magnetic heads, if scratches having various shapes are generated on the surface of the workpiece, the wiring formed thereon is insufficiently etched, causing a defect such as a short circuit. Therefore, the occurrence of scratches with various shapes is monitored by observing the polished or ground wafer surface after grinding or grinding, and if it occurs frequently, the polishing or grinding conditions corresponding to the scratch shape are reviewed. There must be. At the same time, when foreign matter is generated, it may cause a failure such as insulation failure or short circuit of a wiring formed thereon. When foreign objects frequently occur, measures different from scratches, such as cleaning the apparatus, are required. In other words, in a polishing or grinding process for an object to be processed (for example, an insulating film on a semiconductor substrate), foreign substances and scratches having various shapes can be separately monitored and appropriate measures can be taken for each. Necessary.

  However, in any of the above Patent Documents 1 to 4, scratches having various shapes generated on the surface of a workpiece (for example, an insulating film on a semiconductor substrate) when polishing or grinding is performed, and Discrimination and inspection of adhering particulate foreign matter are not considered.

  In addition, the scratches having various shapes have a width W of about 0.2 μm to 0.4 μm and a depth D of about several nanometers to a very deep one of about 100 nm. Then, an operator visually reviews using an electron microscope to discriminate scratches and foreign matters having various shapes, and a great amount of review time is required. For this reason, there is a delay in measures against scratches or particulate foreign matters, and a large amount of wafers continue to be polished in a bad condition, causing a great deal of damage to profits.

  An object of the present invention is to solve the above-mentioned problems when performing polishing or grinding processing such as CMP on an object to be processed (for example, an insulating film on a semiconductor substrate) in semiconductor manufacturing or magnetic head manufacturing. It is an object of the present invention to provide a defect inspection apparatus and method capable of discriminating and inspecting scratches having various shapes generated on the surface and adhering particulate foreign matters.

  Another object of the present invention is to provide scratches having various shapes generated on the surface of an object to be processed (for example, an insulating film on a semiconductor substrate) when polishing or grinding such as CMP is performed. The semiconductor substrate free from the above defects can be manufactured with high reliability and efficiency by making it possible to perform 100% inspection or sufficient frequency sampling inspection for discriminating and inspecting adhering particulate foreign matters An object of the present invention is to provide a method for manufacturing a semiconductor substrate.

  Further, another object of the present invention is to discriminate and inspect concave defects such as thin film-like foreign matters and scratches having a small height and depth, and convex defects of particulate foreign matters having a high height. Thus, it is an object of the present invention to provide a method for manufacturing a semiconductor substrate in which a semiconductor substrate free from the above defects can be manufactured with high reliability and efficiency.

  In order to achieve the above object, the present invention provides a stage on which an object to be inspected is placed, and a position on the surface of the object to be inspected placed on the stage in a direction normal to or near the surface. An epi-illumination system that epi-illuminates illumination light composed of UV light or DUV light from a direction with a desired light beam and oblique illumination of illumination light composed of UV light or DUV light at a location on the surface of the inspection object An illumination optical system having an oblique illumination system and a first reflected light generated from a portion illuminated by the epi-illumination system of the illumination optical system toward a high angle with respect to the surface of the inspection object Of the first high-angle scattered light and the second reflected light generated from the portion illuminated obliquely by the oblique illumination system of the illumination optical system, the second high-angle scattered light directed to the high angle is collected. High-angle imaging optical system and the high-angle imaging light Detection optics having photoelectric conversion means for receiving first and second high-angle scattered light imaged by the system and converting them into first and second luminance signals (S (i), T (i)) And a defect on the object to be inspected based on the correlation between the first luminance signal S (i) and the second luminance signal T (i) converted by the photoelectric conversion means of the system and the detection optical system It is a defect inspection apparatus and method comprising a comparison / determination unit that discriminates i into a concave defect (scratch or thin film-like foreign matter) and a convex defect (particulate foreign matter).

  Further, according to the present invention, in the epi-illumination system of the illumination optical system in the defect inspection apparatus, the epi-illumination light is not applied to the condenser lens so as not to generate stray light from the high-angle condensing optical system. It is configured to irradiate the surface.

  Further, according to the present invention, the detection optical system in the defect inspection apparatus further includes a light shielding means for shielding a specific light image by the first reflected light on a Fourier transform surface of the first reflected light emitted from the location. It is provided with.

  In the comparison / determination unit of the defect inspection apparatus, the correlation may be a ratio (T (i) / S (i), S (i) / T (i)) as the correlation.

  Further, according to the present invention, in the comparison / determination unit in the defect inspection apparatus, data corresponding to a defect size calculated from the first luminance signal S (i) and the second luminance signal T (i) Accordingly, the present invention is characterized in that the concave defect is distinguished from a scratch and a thin film foreign material (in the present invention, the thin film foreign material is also defined as a concave defect because the thickness is very thin).

  Further, according to the present invention, in the comparison / determination unit in the defect inspection apparatus, data corresponding to a defect size calculated from the first luminance signal S (i) and the second luminance signal T (i) It is characterized in that it is configured to discriminate particulate foreign matters which are convex defects based on the size.

  Further, the present invention is configured such that the comparison / determination unit in the defect inspection apparatus can recognize whether the discriminating convex defect has occurred in the circuit pattern area or outside the circuit pattern area. It is characterized by that.

  Further, the present invention is characterized in that the comparison / determination unit in the defect inspection apparatus has display means for displaying information on the identified defect.

  Further, the present invention is characterized in that the comparison / determination unit in the defect inspection apparatus has a display means for displaying information relating to the relationship of the first luminance signal for discriminating defects.

  Further, the present invention is characterized in that the comparison / determination unit in the defect inspection apparatus has display means for displaying information relating to the relationship of the second luminance signal for discriminating defects.

  Further, according to the present invention, the comparison / determination unit in the defect inspection apparatus shows the relationship between the first luminance signal and the second luminance signal converted by the photoelectric conversion means of the detection optical system, and the horizontal axis and the vertical axis. It has the display means which plots and displays on the correlation diagram represented by a logarithmic value, It is characterized by the above-mentioned.

  Further, the present invention provides an illumination optical system in the defect inspection apparatus, wherein a spot on the surface of the object to be illuminated is reflected by the epi-illumination system and a part to be obliquely illuminated by the oblique illumination system is within the field of view of the detection optical system. It is characterized by being configured differently.

The present invention also provides a stage on which an object to be inspected is placed, and UV light or DUV from a direction normal to or near the surface of the stage on the surface of the inspected object placed on the stage. An epi-illumination system for epi-illuminating illumination light composed of light with a desired light beam and obliquely illuminating light of a wavelength different from the illumination light composed of UV light or DUV light with a desired light beam at a location on the surface of the inspection object An illumination optical system having an oblique illumination system for illuminating, and the first reflected light generated from a portion illuminated by the epi-illumination system of the illumination optical system at a high angle with respect to the surface of the inspection object Of the first high-angle scattered light that travels and the second high-angle scattered light that travels toward the high angle out of the second reflected light that is generated obliquely by the oblique illumination system of the illumination optical system. And the light collected by the light collecting optical system. A wavelength separation optical system that separates the wavelength of the first high angle scattered light and the second high angle scattered light, and the first high angle scattered light and the second high angle scattered light separated by the wavelength separation optical system. An imaging optical system that images each of the first luminance signal and the second high-angle scattered light that is imaged by the imaging optical system and receives the first high-angle scattered light and the second high-angle scattered light. Detection optical system having first and second photoelectric conversion means for converting each of the luminance signals, and the first luminance signal and the second photoelectric signal converted by the first photoelectric conversion means of the detection optical system. A defect inspection apparatus and a method therefor, comprising: a comparison / determination unit that discriminates defects on the inspection object based on a relationship between the second luminance signal converted by the conversion means.

  Further, the present invention performs epi-illumination and oblique illumination with illumination light composed of UV light or DUV light with substantially the same light flux on shallow scratches or foreign matters generated on the surface of a polished or ground film. Scattered light generated from shallow scratches and foreign objects by illumination and oblique illumination is received by a detector and converted into luminance signals according to the intensity of each scattered light, and based on the correlation of these converted luminance signals It is a defect inspection method characterized by discriminating shallow scratches from foreign substances.

  Further, the present invention is directed to epi-illumination and oblique illumination of illumination light composed of UV light or DUV light with substantially the same luminous flux against a flat thin film foreign matter or foreign matter generated on the surface of a polished, cleaned or sputtered film. The scattered light generated from the thin-film foreign matter and the foreign matter due to the epi-illumination and oblique illumination is received by the detector and converted into luminance signals according to the intensity of each scattered light, and these converted luminance signals The defect inspection method is characterized in that a thin film-like foreign substance is discriminated from a foreign substance on the basis of the correlation.

  According to the present invention, when a workpiece such as an insulating film is subjected to polishing or grinding such as CMP in semiconductor manufacturing or magnetic head manufacturing, it adheres to scratches having various shapes generated on the surface. There is an effect that it can be discriminated from the particulate foreign matter to be inspected.

  Further, according to the present invention, since the shape of the scratch can be classified in detail, there is an effect that the cause of the failure can be quickly identified.

  In addition, according to the present invention, all or a high frequency sampling inspection can be performed in the flattening polishing step, so that a defect of the polishing apparatus can be quickly found, and as a result, appropriate measures can be taken. Therefore, the yield in the polishing process can be drastically improved.

  DESCRIPTION OF EMBODIMENTS Embodiments of a defect inspection apparatus and method for the purpose of stable operation of a planarization process used in a semiconductor manufacturing process and a magnetic head manufacturing process according to the present invention will be described with reference to the drawings.

  First, a first embodiment of the defect inspection apparatus and method according to the present invention will be described. As shown in FIG. 1, the present invention relates to a defect inspection apparatus 100 that extracts a product or inspects all products during a semiconductor manufacturing process. In the semiconductor manufacturing line, manufacturing conditions are managed by a process management computer 101 via, for example, the network 103 or for each individual manufacturing apparatus (not shown). In the middle of the process, the semiconductor is inspected by a foreign substance inspection apparatus, an optical appearance inspection apparatus, an SEM inspection apparatus, or a human hand. If any abnormalities are found during the inspection, review them using an optical review device, SEM review device, etc., and in some cases, perform further detailed analysis using EDX (energy dispersive X-ray spectroscopy). Determine the cause of the abnormality. After that, the production conditions that caused the abnormality and measures against the manufacturing equipment were taken to improve the yield. Further, data such as the coordinates and dimensions of foreign matters and defects detected by the defect inspection apparatus 100, and data such as the type and category of the identified defects are managed on-line by the yield management system 102.

As shown in FIG. 2, the defect inspection apparatus 100 according to the present invention forms an interlayer insulating film (object to be processed) 22 such as a SiO ₂ film on a Si wafer 21 and performs CMP (Chemical Mechanical Polishing). At this time, the scratch 23 a having a small depth generated on the wafer 10 and the foreign matter 24 are discriminated. Incidentally, under the interlayer insulating film 22 such as the SiO ₂ film, the semiconductor substrate 21 such as the Si substrate is not necessarily present, and there may be a wiring layer. In the CMP process, polishing is performed to flatten the surface of the SiO ₂ film 22. Therefore, scratches 23a that are polishing scratches are generated on the surface of the SiO ₂ film 22 as shown in FIG. Here, the thickness of the SiO ₂ film 22 is t, the width of the scratch 23a is W, and the depth is D. As for the rough dimension of the scratch 23a, W is about 0.2 μm to 0.4 μm. The depth D is about several nanometers to about 100 nm even for very deep objects. As described above, the scratch 23a generated by CMP is characterized by a very shallow depth with respect to the width. FIG. 2A shows dimensional parameters of the foreign matter 24. Here, the foreign material 24 is modeled as a granular material having a diameter Φ. The actual foreign matter 24 is not such a beautiful spherical shape, but the scratch 23a has a depth D of about several nm to several + nm with respect to the width W (about 0.2 μm to 0.4 μm). (Particulate foreign matter) 24 indicates that the width and height are not significantly different from those of the scratch 23a. The present invention pays attention to the characteristic dimension ratio of the scratch 23a.

  Next, a first example of a surface inspection apparatus such as a scratch for realizing the first embodiment will be described with reference to FIGS. That is, as shown in FIG. 1, the first embodiment of the surface inspection apparatus includes a stage 15 on which a position coordinate is measured and travel control is performed in the X and Y directions, and a wafer 10 as an inspection object is placed. A plurality of light sources 2a that are composed of light sources (not limited to laser light sources) such as an Ar laser, a nitrogen laser, a He—Cd laser, and an excimer laser having a wavelength of 488 nm (blue wavelength) and output light of different wavelengths. 2b, and the reflecting optical mirror 1a, 4b, 4c, an illumination optical system 1, a condensing lens 6, a beam splitter 7 that separates by wavelength, a photomultiplier, a CCD camera, a CCD sensor, a TDI sensor, and the like. An analog luminance signal output from each of the detection optical system 5 including the photoelectric converters 8a and 8b and the photoelectric converters 8a and 8b is converted into a digital luminance signal. / D conversion units 16a, 16b, storage units 17a, 17b that temporarily store digital luminance signals obtained from each of the A / D conversion units 16a, 16b, and a calculation processing unit 9 configured as described above, Based on the position coordinates measured from the stage 15, the stage controller 14 that controls the travel of the stage 15, the stage controller 14 is controlled, the arithmetic processing unit 9 is further controlled, and the inspection result obtained from the arithmetic processing unit 9 is obtained. It is comprised from the whole control part 30 to receive. As the light sources 2a and 2b, in order to discriminate and detect the minute foreign matter 24 and the scratch 23 generated on the CMP insulating film 22, it is preferable that the wavelength is as short as possible, like an excimer laser light source. That is, as the light source 2a, for example, a laser light source that emits a laser beam of 488 nm or 365 nm, and as the light source 2b, a double wave (532 nm) or quadruple wave (266 nm) DUV laser light of a YAG laser, or a KrF excimer laser is used. A laser light source that emits light can be used. The UV light or DUV light emitted from the light source 2a is not directly irradiated onto the surface of the condenser lens 6, and the wafer surface (insulating film subjected to CMP) is passed through the reflecting mirror 4a and the reflecting mirror 4c. Is irradiated from the normal direction or the vicinity thereof. This is called epi-illumination 12. Alternatively, the UV light or DUV light emitted from the light source 2b irradiates the wafer surface (the surface of the insulating film subjected to CMP) from an oblique direction via the reflection mirror 4b. This is referred to as oblique illumination 11. In the first embodiment, epi-illumination and oblique illumination are realized using two independent and independent light sources 2a and 2b and a plurality of reflecting mirrors 4a to 4c. In addition, an optical path switching mechanism (not shown) that switches the optical path of the UV light or DUV light emitted from the light source 2b to the mirror 4b and the mirror 4c may be used. Further, the number of reflecting mirrors and the presence or absence of an optical path switching mechanism are not questioned.

  Further, in the illumination optical system 1, a detection optical part is detected on the wafer surface where the epi-illumination light 12 is incident on the wafer surface and on the wafer surface where the oblique illumination light 11 is obliquely illuminated by the oblique illumination system. By making them different in the field of view of the system 5, the incident illumination light 12 and the oblique illumination light 11 can have the same wavelength. However, in this case, it is necessary to install the light receiving surfaces of the photoelectric converter 8a and the photoelectric converter 8b so as to correspond to the difference in the irradiation location on the wafer surface.

  As described above, the illumination optical system 1 does not directly irradiate the surface of the condenser lens 6, and the normal direction with respect to the CMP surface on which the CMP is performed on the insulating film 22 on the wafer 10, or on it. Two systems of illumination (epi-illumination and oblique illumination) 11 and 12 from a near direction and an oblique direction (an angle of about 30 ° or less) close to the wafer horizontal plane may be realized. In the case of the epi-illumination 11, as shown in FIG. 1, the pseudo epi-illumination may be as close to the vertical direction as possible.

  Next, the detection procedure will be described. Detection is performed twice for one wafer 10 by switching the illumination direction. Specifically, first, the CMP of the insulating film 22 on the wafer 10 is performed without directly irradiating the surface of the condenser lens 6 with the epi-illumination light 12 made of UV light or DUV light emitted from the light source 2a. Irradiate the surface. Then, the specularly reflected light component generated from the insulating film 22 was removed without generating stray light reflected from the fine surface roughness of the surface of the condenser lens 6 or the extremely fine foreign matter adhering to the surface. In this state, only the shallow shallow scratches 23 a generated by CMP on the insulating film 22 and the scattered light (low-order diffracted light component) emitted from the foreign matter 24 are collected by the condenser lens 6 and pass through the beam splitter 7. For example, the light is received by a light receiving surface of a photoelectric converter 8a composed of a CCD, TDI sensor or the like. The output of the photoelectric converter 8a is A / D converted by the A / D conversion unit 16a to obtain the luminance value S (i) for each defect i, and then written in the storage unit 17a.

  At the same time, oblique illumination light 11 emitted from the light source 2b and made of UV light or DUV light having a wavelength different from that of the light source 2a is applied to the same coordinate position as the epi-illumination light 12 on the wafer surface. The overall control unit 30 controls the movement of the stage 15 to switch the irradiation direction using an optical path switching mechanism (not shown), and the oblique illumination light 11 is the same as the incident illumination light 12 on the wafer surface. Irradiation may be performed in a position coordinate system.

  Then, in the state where the specularly reflected light component generated from the insulating film 22 is removed, the scattered light (low level) emitted from the very shallow fine scratch 23a and foreign matter (particulate foreign matter) 24 generated by CMP on the insulating film 22 is removed. Only the next diffracted light component) is collected by the condenser lens 6 and received by the photoelectric converter 7b through the beam splitter 7, for example. Then, the output of the photoelectric converter 7b is A / D converted by the A / D converter 16b to obtain the luminance value T (i) for each defect i, and then once written in the storage unit 17b.

Next, the comparison calculation unit 18 detects the detection luminance value S (i) for each defect i by the epi-illumination 12 stored in the storage unit 17a and the detection for each defect i by the oblique illumination 11 stored in the storage unit 17b. A ratio R (i) with the luminance value T (i) is calculated. If the calculated luminance ratio R (i) is larger than a preset threshold value (judgment reference value: the discrimination line 20 shown in FIG. 5), the comparison calculation unit 18 generates a foreign object 24, and if it is smaller, a very shallow fine scratch 23a. Discriminate and output to the overall control unit 9. As described above, the scratch 23a generated by CMP is extremely shallow and fine, and therefore, faint stray light generated from the surface of the condensing lens 6 when the surface of the condensing lens 6 is irradiated with the incident illumination light 12, for example, When the photoelectric converter 7a receives light, it becomes difficult to distinguish it from the scattered light from the scratch 23a. Therefore, the surface of the condenser lens 6 is not irradiated with the epi-illumination light 12.

  In the first embodiment, the detection by the epi-illumination light 12 and the detection by the oblique illumination light 11 are performed simultaneously. However, the detection by the epi-illumination light 12 is performed first, and the detection by the oblique illumination 11 is performed later. However, the detection with the oblique illumination light 11 may be performed first, and the detection with the epi-illumination light 12 may be performed later. In the first embodiment, the detected luminance value T (i) obtained by the oblique illumination 11 that is the second detection is once written to the storage unit 17 after A / D conversion, and the second detected luminance value T ( Without storing i), the present invention can be realized even if the comparison operation unit 18 refers to the detected luminance value S (i) of the first incident illumination 12 already stored at the same time as the detection and performs the luminance comparison calculation. It is possible to do.

  Next, the principle of discrimination for realizing the above-described embodiment according to the present invention will be described in detail with reference to FIGS. In the present invention, discrimination is performed by irradiating one defect with a light beam d from two different angles (for example, epi-illumination 12 and oblique illumination 11). First, the incident illumination light 12 is irradiated with the light flux d from the normal direction of the wafer surface or the vicinity thereof without directly irradiating the surface of the condenser lens 6. Next, the oblique illumination light 11 is irradiated with a light beam d from an angle close to the horizontal direction with respect to the wafer surface. It does not matter which one of the epi-illumination 12 and the oblique illumination 11 is performed first. Discrimination is performed by comparing the intensities of scattered light emitted from the defects 23a and 24 obtained in the two-way illumination of the light beam d. The intensity of scattered light from the defects 23a and 24 is emitted according to the amount of light source received by the defects 23a and 24. As shown in FIG. 3, it may be considered that the amount of light source received by the defects 23a and 24 is substantially proportional to the projected area of the defect dimension in the light source incident direction.

  In the case of the scratch 23a which is a concave defect, the projected area is substantially proportional to the width W in the epi-illumination, and is substantially proportional to D ′ in the oblique illumination irradiated at a shallow angle of about 30 ° or less. However, since the depth D of the scratch 23a is very shallow compared to the width W, the oblique illumination projection length D ′ is much shorter than the incident illumination projection length W ′. Therefore, the amount of light source received by the scratch 23a is weaker in the oblique illumination 11 than in the epi-illumination 12, and as a result, the amount of scattered light emitted from the scratch 23a is weaker in the oblique illumination 11. . In contrast, in the case of a foreign matter (particulate foreign matter) 24 that is a convex defect, the projection lengths Φ of the oblique illumination 11 and the epi-illumination 12 are substantially equal, so the amount of scattered light emitted from the foreign matter 24 is Compared with epi-illumination and oblique illumination, there is no big difference. Therefore, as shown in FIG. 4, the detected brightness values S (i) and T (i) of the scattered light by the epi-illumination 12 and the oblique illumination 11 are compared, and the oblique illumination 11 is more epi-illuminated. If it is smaller than 12, it becomes possible to discriminate the scratch 23a, an object having the same or oblique illumination as a foreign matter (particulate foreign matter) 24.

  Further, since the thin-film foreign matter 23b is also very thin, the detection luminance value T (i) of the scattered light by the oblique illumination 11 is the detection luminance value S (i of the scattered light by the epi-illumination 12 as in the scratch 23a. ), And can be regarded as a concave defect.

  A graph of an example of the discrimination result is shown in FIG. This is a graph in which the horizontal axis represents the detected luminance value S (i) during epi-illumination and the vertical axis represents the detected luminance value T (i) during oblique illumination. In this case, the area below the discrimination line 20 in the figure is the area of the scratch 23a, and the area above is the area of the foreign matter 24. However, as is apparent from FIG. 5, in practice, the detected luminance value S (i) in the epi-illumination is simply compared with the detected luminance value T (i) in the oblique illumination. Even if the ratio is taken, the discrimination line (determination threshold value) 20 cannot be drawn (set), and it is difficult to discriminate the foreign matter 24 from the scratch 23a. Therefore, using the detected brightness value S (i) at the time of epi-illumination and the detected brightness value T (i) at the time of oblique illumination according to the present invention, specifically, the foreign matter (particulate foreign matter) 24 and the scratch 23a An example of a technique for discriminating between will be described later.

By the way, since the insulating film (for example, SiO ₂ film) 22 in which the scratch 23a is generated by CMP is transparent to light, specular reflection light from the lower layer including light interference is generated. As shown in FIG. 1, for example, by installing a reflection mirror 4c outside the field of view of the condenser lens 6, regular reflection light (including optical interference light) from the surface of the insulating film 22 and its lower layer is collected. It is necessary to devise a way to go outside the field of view of the optical lens (objective lens) 6 so as not to be detected by the photoelectric converter 8a, for example.

  Of course, in the case of the oblique illumination 11, as shown in FIG. 1, since it is irradiated at a very shallow angle by the reflection mirror 4b, regular reflection light (including light interference light) from the surface of the insulating film 22 and its lower layer is also included. ) Goes out of the field of view of the condenser lens 6 and is not detected by the photoelectric converter 8b.

  If a light source that emits broadband light or white light is used as the light source 2, the problem of optical interference between the regular reflection light from the surface of the insulating film 22 and the regular reflection light from the lower layer does not occur. However, in order to obtain intense scattered light from the fine scratches 23a on the insulating film 22 (particularly the depth D is shallow) and the foreign matter 24, it is preferable to use UV light or DUV light as illumination light.

  Next, an embodiment of a method for installing the reflection mirror 4c will be described with reference to FIG. This is a technique for detecting defects with high sensitivity by preventing stray light in the dark field detection system. The inspection of the scratch 23a requires illumination from a direction close to the normal to the surface of the wafer 10, as can be understood from the principle described above.

  However, in the case of epi-illuminating UV light or DUV light, when the epi-illumination light is transmitted through the condenser lens 6 to illuminate the wafer 10, so-called stray light is generated, resulting in noise in the detected image. It will end up. Specifically, the scattered light generated from fine polishing marks on the surface of the condensing lens 6 and dust adhering to the condensing lens 6 becomes stray light. For this reason, when the minute scattered light from the defects 23a and 24 is received by the photoelectric converter 8a and observed, this stray light becomes fatal. That is, the scattered light from the extremely small scratch 23a is buried in noise caused by stray light and cannot be detected.

  Therefore, in the present invention, as shown in FIG. 6, strong incident light is not applied to the surface of the condenser lens 6, and the wafer 10 (the surface of the interlayer insulating film 22 (CMP surface) and its lower layer) are not irradiated. The 0th-order diffracted light, which is a specularly reflected light component (including the interference light component) from the surface of the wiring layer and the like, the surface of the scratch 23a, and the surface of the foreign material 24, is prevented from entering the pupil of the condenser lens 6, that is, the NA. It is necessary to provide the reflection mirror 4c.

  In FIG. 6A, a small reflecting mirror 4c1 is arranged between the wafer 10 and the condenser lens 6 and substantially on the normal line of the wafer 10, so that the incident illumination light 12a is not irradiated on the surface of the condenser lens 6. Is incident on the small reflecting mirror 4c1 from the lateral direction and reflected, and the specularly reflected light component (including the interference light component) from the wafer 10 is reflected by the reflecting mirror 4c1 and enters the pupil of the condenser lens 6. Of the scattered light (first-order or higher-order diffracted light component) from the scratch 23a or the foreign matter 24 without being incident, the scattered light (low-order diffracted light component) in the region indicated by the oblique lines (in a planar shape in a ring shape) is collected. A method of making the light lens 6 enter the pupil will be described. The small reflecting mirror 4c1 has an almost elliptical outer shape. This is called scattered light detection by vertical illumination. However, this method is not preferable because the central portion of the condenser lens 6 loses its role as a lens.

  6B, the reflecting mirror 4c2 is disposed between the wafer 10 and the condenser lens 6 and outside the condenser lens 6, and the incident illumination light 12b is provided on the surface of the condenser lens 6. So that it is incident on the reflecting mirror 4c2 from the lateral direction so that it is not irradiated, and the specularly reflected light component from the wafer 10 is out of the pupil of the condenser lens 6, and the scattered light from the scratch 23a and the foreign matter 24 The method of making the scattered light of the area | region shown with a diagonal line enter into the pupil of the condensing lens 6 is shown. When the reflection mirror 4c2 is expanded in the circumferential direction, the illumination light illuminated by the reflection mirror 4c2 becomes annular illumination. In this case, for example, if three reflection mirrors 4c2 are provided at intervals of 120 degrees in the circumferential direction, and each of the three illumination lights 12b is incident from between each of these three reflection mirrors 2c2, a ring is formed from the three directions. It is also possible to perform band illumination. However, as shown in FIG. 6B, when the reflecting mirror 4c2 is made a part, it becomes a part of the illumination in the annular illumination. This is called scattered light detection by pseudo vertical illumination. This method is very effective because the entire visual field (pupil) of the condenser lens 6 is used. However, the luminous flux of the oblique illumination light 11 also needs to be matched to the luminous flux of the epi-illumination light 12b including the number of points.

  Further, in FIG. 6C, a small reflecting mirror or half mirror 4c3 is disposed in the vicinity of the optical axis above the condensing lens 6, and the condensing lens 6 having an opening 50 formed in the center is disposed. The vertical illumination light 12a reflected by the reflecting mirror or the half mirror 4c3 is irradiated on the insulating film CMP surface on the wafer 10 through the opening 50 without irradiating the surface of the condenser lens 6, and from the wafer 10. The specularly reflected light component is shielded by a spatial filter (light shielding element) 51 provided on the Fourier transform surface, and the scattered light obtained through the condensing lens 6 of the scattered light from the scratch 23a and the foreign matter 24 is converted by the photoelectric converter 8a. A method for receiving light will be described.

  6D, the incident illumination light 12a is transmitted through the central portion of the half mirror 52 and is perpendicular to the CMP surface of the wafer 10 through the opening 50 of the condenser lens 6, as in FIG. 6C. Illuminated, the specularly reflected light from the wafer 10 is shielded by a spatial filter (light-shielding element) 53 provided on the Fourier transform surface, and the scattered light obtained through the condensing lens 6 of the scattered light from the scratch 23a and the foreign matter 24 is A method in which light is reflected by the peripheral portion of the half mirror 52 and received by the photoelectric converter 8a will be described. In addition, you may comprise the peripheral part of the half mirror 52 with a reflective mirror.

  As described above, in FIGS. 6C and 6D, stray light is generated from the surface of the condenser lens 6 by forming the opening 50 in the center of the condenser lens 6 as in FIG. 6A. Without this, it becomes possible to detect vertical illumination and scattered light from the vertical direction. Therefore, no matter how the direction of the scratch 23a is formed in the horizontal plane, the scattered light generated from the edge of the very shallow scratch 23a can be received by the photoelectric converter 8a relatively uniformly. The detected luminance value S (i) can be obtained. Further, in order to obtain diffracted light having a strong directivity in a direction perpendicular to a large scratch (not shown) that is a linear pattern, vertical illumination is preferable to pseudo-vertical illumination. However, the embodiment of FIGS. 6C and 6D is not so preferable because the function of the condensing lens 6 is deteriorated because the opening 50 is formed in the central portion of the condensing lens 6.

  By the way, in the case of the scattered light detection by the vertical illumination of FIG. 6A, the incident light passes under the lens 6 and is clearly not irradiated on the surface of the condenser lens 6, and stray light does not occur. Further, the specularly reflected light from the wafer 10 is reflected by the reflecting mirror 4c1, and therefore does not enter the pupil of the condenser lens 6. Further, the vertical illumination shown in FIGS. 6C and 6D is the same. Further, also in the case of detecting scattered light by pseudo vertical illumination in FIG. 6B, obviously incident light does not pass through the condenser lens 6. Further, since the reflection mirror 4 c 2 is disposed outside the NA of the condenser lens 6, the regular reflection light component from the wafer 10 does not enter the pupil of the condenser lens 6. That is, in any method, incident light that has high light intensity and is likely to generate stray light is not irradiated on the surface of the condenser lens 6, and epi-illumination is realized so that regular reflection light from the wafer does not enter the condenser lens 6. is doing. For this reason, stray light hardly occurs, and a detection image with a high S / N ratio can be obtained from the scratch 23 a and the foreign matter 24 generated on the CMP surface where the interlayer insulating film 22 is subjected to CMP. Note that since the interlayer insulating film 22 is transparent to light, when the incident illumination is applied, the light regularly reflected from the lower layer returns. As described below, the condenser lens (objective lens) 6 is used. Thus, the scratch 23a and the foreign matter 24 can be detected by a signal obtained from the photoelectric converter 8a without affecting the detection of scattered light from the scratch 23a and the foreign matter 24.

  Furthermore, the epi-illuminations 12a and 12b shown in FIG. 6 are not only for the reason for solving the stray light, but also particularly easy to receive a component having a strong scattered light intensity distribution from the scratch 23a. High detection sensitivity can be obtained. This is because the low-order diffracted light component is relatively strong in the scattered light intensity from the scratch 23a. That is, if illumination is performed from the vicinity of the normal line of the wafer surface, low-order diffracted light components are reflected from the wafer 10 and are easily collected by the condenser lens 6. However, for example, regular reflection light (0th order diffracted light) from the base of the insulating layer or the surface of the insulating layer needs to be completely shielded from light or not incident on the pupil of the condenser lens 6.

  As a result, it is possible to detect the scratch 23a with higher sensitivity than when using only the oblique illumination 11. Thus, by using only the vertical illumination 12a or the pseudo vertical illumination 12b, it is possible to realize a highly sensitive inspection of the scratch 23a.

  By the way, if the reflection mirror 4c1 is formed in an almost elliptical shape so that the imaging characteristics of the lens 6 and the like are not affected even if the reflection mirror 4c1 is arranged in the NA of the condenser lens 6, FIG. The scattered light in the region (a zone region in plan view) indicated by the oblique lines in (a) can be condensed by the condenser lens 6 to form an image. However, if the presence of the reflection mirror 4c1 within the NA of the condenser lens 6 adversely affects the imaging characteristics, a mechanism for retracting the reflection mirror 4c1 out of the NA during vertical illumination is required. In the case of semiconductor inspection, it is necessary to eliminate as much as possible dust generated from the defect inspection apparatus. From this point of view, it is not preferable to provide the movable mechanism above the wafer. However, even in such a case, the pseudo vertical illumination 12b may be used. In the case of the quasi-vertical illumination 12b, the reflecting mirror 4c2 is outside the NA, so the imaging characteristics are never adversely affected, and there is no need to provide a separate retraction mechanism.

  Further, when the surface inspection device such as a scratch according to the present invention is used as a foreign matter inspection device using only oblique illumination, vertical illumination is unnecessary, and therefore the reflecting mirror 4c1 shown in FIG. It is also possible to effectively collect the scattered light generated from the foreign matter by using all NA of the condenser lens 6 and receive it by the photoelectric converter 8b. However, in order not to retract the reflecting mirror 4c1 and eliminate the generation of dust, the pseudo vertical illumination 12b whose scratch detection accuracy is somewhat lowered may be used as the vertical illumination of the surface inspection apparatus. In addition, when the method shown in FIGS. 6C and 6D is used as the vertical illumination, it can be applied by stopping the vertical illumination even when used as a foreign matter inspection apparatus using only oblique illumination. It becomes. Furthermore, when used as a foreign matter inspection apparatus using only oblique illumination, if a foreign matter on a memory cell on which a periodic wiring pattern is formed is detected, the diffraction pattern based on the diffracted light from the periodic wiring pattern is shielded. Therefore, the spatial filters 51 and 53 may be replaced with linear spatial filters.

Next, in the comparison calculation unit 18 or the like, the luminance signal S (i) for each defect i by the epi-illumination 12 and the luminance signal T (i) for each defect i by the oblique illumination 11 stored in the storage units 17a and 17b are stored. Based on FIG. 7, a method for estimating the defect size will be described. 7A and 7B show waveforms 301 and 302 of luminance signals S (i) and T (i) detected from the foreign matter 24, the scratch 23a, and the thin film-like foreign matter 23b. The luminance signal waveform 302 shown in FIG. 7B is reduced at a level of 303 as shown in FIG. 7C due to the dynamic range of the detectors (photoelectric converters) 8a and 8b. Therefore, interpolation is performed based on the plot point 304, and the volume is obtained by integrating the interpolated signal waveform in two dimensions. Since the luminance signal shown in FIG. 7A is not narrow, the volume is obtained by integrating the luminance signal waveform in two dimensions. Since the obtained volume value (two-dimensional integral value) and the defect size have a correlation, the estimated data corresponding to the defect size can be obtained by multiplying the correction coefficient.

  FIG. 8 shows the size of the foreign material (μm) estimated as the estimated data for the foreign material 2901 in the inspection apparatus 18 according to the present invention, for example, and the size actually measured by the SEM (μm). Show the relationship. As shown in FIG. 8, there are different correlations as indicated by reference numerals 2902 and 2903 depending on a plurality of process processing (for example, CMP) processes on the wafer 10. Therefore, the correction coefficient changes according to the surface condition of the wafer. Therefore, it is necessary to obtain in advance a correction coefficient corresponding to the process step (wafer surface state) based on SEM measurement.

Further, FIG. 9A shows a foreign substance size (μm) estimated from a luminance signal waveform and a size measured by SEM for a defect 3101 in a front-end process wafer (wafer in a transistor forming process which is an initial process). 3102 indicates that there is a correlation with correlation coefficient R ² = 0.7945. As described above, in the transistor formation process, microdefects of 0.1 μm to 0.4 μm affect the performance of the transistor, and it is understood that such microdefects have a correlation. The correlation coefficient R is expressed by the following equation (Equation 1).

_{R = (NΣx i y i -} (Σx i) (Σy i)) / (√ (NΣx i 2 - (Σx i) 2) (NΣy
_i ² − (Σy _i ) ² )) (Equation 1)
However, x and y indicate variables.

Further, FIG. 9B shows a foreign substance size (μm) estimated from a luminance signal waveform and a size measured by SEM for a defect 3101 in a back-end process wafer (a wafer in a wiring forming process which is a later process). 3102 indicates that there is a correlation with correlation coefficient R ² = 0.7147. In this way, in the wiring formation process, fine foreign matter up to about 5 μm of 0.3 μm or more further affects the wiring, and it can be seen that such fine foreign matter also has a correlation. In the wiring process, minute foreign matters having a size of 0.3 μm or less are erased because their importance decreases.

  Next, the defect inspected by the inspection apparatus according to the present invention will be described with reference to FIG. As defects on the surface subjected to CMP, convex defects 24 based on normal foreign matters (about 0.1 μm to 5 μm) and scratches (width W is about 0.2 μm to 0.4 μm, depth D is several nm to several numbers). And a flat defect 23b to which a thin defect (a diameter of about 0.5 μm to 2 μm and a thickness of about several nm to several + nm) is attached.

Further, from the correlation diagram (correlation coefficient R ² = 0.3847) between the size (μm) from the luminance signal and the size (μm) based on the SEM measurement, these convex defect 24, concave defect 23a and flatness are obtained. It was found to have a different correlation with the defect 23b.

  Further, the size of the defect estimated from the luminance signals S (i) and T (i) detected by the epi-illumination and / or the oblique illumination of the concave defect 23a such as a scratch and the flat defect 23b such as a thin film-like foreign substance. It was found that it is possible to discriminate based on this.

  Further, by discriminating whether the convex defect 24 such as a foreign substance and the concave defect 23a such as a scratch are within the circuit pattern area or outside the circuit pattern area, the convex shape of the foreign substance or the like is discriminated. It becomes possible to discriminate the fatality with respect to the circuit pattern of the defect 24 and the concave defect 23a such as a scratch.

  Therefore, these discrimination methods that are arithmetically processed in the comparison arithmetic unit 18 and the like will be described with reference to FIG. First, in step S111, the luminance signal S (i) for each defect i by the epi-illumination 12 detected from the photoelectric converter 8a is stored in the storage unit 17a after A / D conversion by the A / D converter 16a. At the same time or after that, in step S112, the luminance signal T (i) for each defect i by the oblique illumination 11 detected from the photoelectric converter 8b is A / D converted by the A / D converter 16b, and then stored in the storage unit 17b. To remember. In step S113, the comparison calculation unit 18 determines the luminance signal S (i) for each defect i detected by the epi-illumination stored in each of the storage units 17a and 17b and the luminance for each defect i detected by the oblique illumination. With the ratio R (i) to the signal T (i), the unevenness (b / a) shown in FIG. 12 is obtained by the following equation (2).

  Note that FIG. 12 is a logarithmic table because both the horizontal axis and the vertical axis are represented by logarithms. In FIG. 12, the direction of the arrow 121 from the lower left to the upper right corresponds to the defect size, and the arrow 122 perpendicular to the arrow 121 is indicated by the degree of irregularity (b / a) of the defect. The unevenness degree (b / a) of the defect is indicated by the ratio of the vertical dimension b to the horizontal dimension a shown in FIG. However, the unevenness of the defect based on the ratio of the luminance signal (T (i) / S (i)) and the integrated value of the luminance signals (S (i), T (i)) The discrimination of the defect size based on the product of the corresponding correction factors does not necessarily require the logarithm of the luminance signal.

R (i) = T (i) / S (i) = b / a (Equation 2)
Here, i is an identification number assigned to each defect in order to evaluate a plurality of defects. In addition, since one defect may be detected as a plurality of defects depending on the size of the light beam d and the pixel size of the photoelectric converter 7, an expansion process (connection process) is performed on a signal indicating a defect detected in the vicinity. ) Needs to be converted into a signal indicating one defect. For this reason, the identification number i assigned to each defect is given to a signal indicating one defect subjected to the connection process.

  Furthermore, in step S114, the comparison calculation unit 18 determines that the convexity such as particulate foreign matter is present if the calculated luminance ratio R (i) is larger than a preset threshold value (judgment reference value: the discrimination line 20 shown in FIG. 5). If it is small, it is determined as a concave defect 23 such as a scratch or a thin film-like foreign substance. In this embodiment, the detected luminance T (i) at oblique illumination is divided by the detected luminance value S (i) at epi-illumination, but conversely, the detected luminance value S (i at epi-illumination). ) May be divided by the detected luminance value T (i) during oblique illumination. In this case, if the ratio R (i) is larger than a preset threshold value (judgment reference value: discrimination line 20 shown in FIG. 5), it is a concave defect 23 such as a scratch and a thin film-like foreign matter, and if it is smaller, it is a convexity such as a foreign matter. It can be distinguished from the defect 24.

  Next, in step S115, the overall control unit 30 performs data corresponding to the defect size based on the unevenness (b / a) obtained in step S113 and the process information of the wafer 10 obtained from the process management computer 101. A correction coefficient for estimating is calculated.

  Next, in step S116, the luminance signal S (i) for each defect i detected by the epi-illumination stored in each of the storage units 17a and 17b by the comparison calculation unit 18, the overall control unit 30, and the like, and the oblique illumination Based on the luminance signal T (i) for each defect i detected by the above, a volume value is obtained by two-dimensionally integrating the respective luminance signal waveforms, and the volume value calculated by the overall control unit 30 is obtained. By multiplying the surface condition (which can be obtained as process information from the process management computer 101) and the degree of unevenness (b / a) by a correction coefficient, an estimated value of the size (estimated according to the size) Data) (μm) is calculated.

  Next, in step S117, based on the data according to the size of the defect estimated in step S115 by the comparison calculation unit 18, the overall control unit 30, etc., as shown in FIG. It can be distinguished from the thin film-like foreign matter 23b. As shown in FIG. 12, the waveform of the luminance signal S (i) by epi-illumination is integrated two-dimensionally to obtain a volume value, and the obtained volume value is multiplied by the correction coefficient (according to the size). It is also possible to discriminate between the scratch 23a and the thin film-like foreign material 23b using the estimated data).

By the above, it becomes possible to discriminate the scratch 23a which is a concave defect, and the thin-film-like foreign material 23b.

  Next, in the overall control unit 30, it is possible to discriminate the normal particulate foreign matter 24 as the convex defect discriminated in step S114. Furthermore, when it is necessary to discriminate between the discriminated particulate foreign matters, in step S118, by using the estimated size of foreign matter (estimated data corresponding to the size) obtained from step S116, FIG. It becomes possible to discriminate between large and small from the relationship shown.

  Further, in step S119, the comparison operation unit 18 and the overall control unit 30 etc., as shown in FIG. 14, remove the network 103 from the CAD system (not shown) for the particulate foreign matter 24 and the scratch 23a having a small size. The particulate foreign matter 24 and the scratch 23a are generated on the basis of the circuit pattern array information obtained on the wafer 10 or the circuit pattern array information obtained based on the circuit pattern image signals detected by the detectors 8a and 8b. By discriminating between occurrences on the circuit pattern and outside the circuit pattern, it is possible to determine the fatality of the foreign matter 24 and the scratch 23a with respect to the circuit pattern. That is, the case where the foreign matter 24 having a small defect size is generated on the circuit pattern is classified as category 1, the case where the particulate foreign matter 24 is generated outside the circuit pattern is classified as category 2, and the scratch 23a having a small defect size is classified. Is generated on the circuit pattern is classified as category 3, the case where the scratch 23a is generated outside the circuit pattern is classified as category 4, and the case where a thin foreign material having a large defect size is generated is classified as category 5. can do. In this way, the overall control unit 30 can classify the category at least for each process, so that it can be used to investigate the cause of the defect as well as to evaluate the fatality of the defect. It becomes possible. When the circuit pattern arrangement information is obtained based on the image signal of the circuit pattern detected by the detectors 8a and 8b, the luminance signal S (i) and T (i) for the defect is detected by the detector 8a. , 8b, for example, by repeating chip comparison or die comparison, it is possible to erase and extract the image signal of the repeated circuit pattern.

  Next, the overall control unit 30 displays on the display device 33 the detected brightness value S (i) during the epi-illumination and the oblique illumination during the particulate illumination (indicated by ◯) and scratches (indicated by △). FIG. 15 and FIG. 16 show correlation diagrams with the detected luminance value T (i). As shown in FIG. 16, both the luminance values S (i) and T (i) are logarithmically compared to the case where the foreign matter 24, the scratch 23a, and the like are compared with those displayed on the normal scale shown in FIG. Can be easily distinguished, and it becomes easy to set a threshold value (discrimination line 20) for discriminating both on the screen. As shown in FIG. 16, when the horizontal axis and the vertical axis are logarithmic, the correlation line 161 indicating the particulate foreign matter 24 and the correlation line 162 indicating the scratch 23a and the like are parallel lines.

Next, a defect map displayed on the screen of the display device 33 by the overall control unit 30 will be described with reference to FIG. FIG. 17A shows a state in which the foreign matter map on the wafer in the predetermined CMP process, which is the inspection result discriminated in step S114 shown in FIG. Similarly, FIG. 17B shows a state in which the scratch map on the wafer in the predetermined CMP process, which is the inspection result discriminated in step S117 shown in FIG. Similarly, FIG. 17C shows a state in which the thin film-like foreign matter map on the wafer in the predetermined CMP process is displayed on the screen of the display device 33, which is the inspection result discriminated in step S117 shown in FIG. . From each of these foreign matter map, scratch map, and thin film-like foreign matter map, it is possible to know the generation distribution of particulate foreign matter, scratch, and thin film-like foreign matter on the wafer.

It is a schematic block diagram which shows 1st Embodiment of the defect inspection apparatus which concerns on this invention. It is a figure which shows the shape parameter of the scratch and foreign material which generate | occur | produce on an insulating film by CMP etc. which concern on this invention. It is a figure for demonstrating incident light projection length when the light beam d is irradiated to the scratch and foreign material which concern on this invention. It is a figure which shows the discrimination principle of the scratch which concerns on this invention, and a particulate foreign material. It is a figure which shows one Example of the discrimination | determination result of a scratch and particulate foreign material based on this invention. It is a figure which shows the Example of the vertical irradiation which concerns on this invention, and pseudo | vertical vertical illumination. It is a figure which shows the luminance signal waveform detected with the detection optical system which concerns on this invention. It is a correlation diagram showing the foreign matter generated on the CMP surface of the wafer according to the present invention by the correlation between the foreign matter size (μm) estimated by the defect inspection apparatus and the SEM measurement size (μm) measured by SEM. In the present invention c), the size (μm) from the luminance signal in the back-end process wafer (front-end process wafer (wafer in the initial process step) related to the latter stage) is plotted on the horizontal axis, and the SEM measurement size (μm) is plotted on the horizontal axis. It is the correlation diagram which plotted the foreign material generation | occurrence | production state at the time of setting to a vertical axis | shaft. The convex defect (particulate foreign matter) and the concave defect (scratch, thin film foreign matter) generated on the CMP of the wafer according to the present invention are measured by the size (μm) from the luminance signal detected by the defect inspection apparatus and SEM. It is a correlation diagram shown by the correlation with the long SEM measurement size (μm). It is a figure which shows one Example of the discrimination processing flow of the scratch which concerns on this invention, a thin-film-like foreign material, and a particulate foreign material (normal foreign material). Scratch, thin film foreign matter based on the degree of unevenness (b / a) and size based on the relationship between the luminance signal S (i) by epi-illumination and the luminance signal T (i) by oblique illumination showing the basic idea of the present invention FIG. 6 is a correlation diagram for explaining that particulate foreign matters (normal foreign matters) are discriminated. It is explanatory drawing of an unevenness | corrugation degree. It is explanatory drawing for obtaining the inspection result classified into the categories 1-5 so that it can discriminate | determine about the fatality of the defect which concerns on this invention. It is a figure which shows the distribution of the particulate foreign material and scratch based on the relationship between the luminance signal S (i) by epi-illumination and the luminance signal T (i) by oblique illumination according to the present invention. It is a figure which shows the distribution of the particulate foreign material based on the relationship between the logarithm value of the luminance signal S (i) by epi-illumination and the logarithm value of the luminance signal T (i) by oblique illumination according to the present invention. It is a figure which shows the wafer map which shows distribution of each defect discriminated by the defect inspection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Illumination optical system, 2a, 2b ... Light source, 4b, 4c, 4c1-4c3 ... Reflection mirror, 5 ... Detection optical system, 6 ... Condensing lens (including an imaging optical system), 7 ... Beam splitter, 8a, 8b: photoelectric converter (CCD, TDI sensor), 9: arithmetic processing unit, 10: inspection object (wafer), 11: oblique illumination light, 12: epi-illumination light, 12a: vertical illumination light, 12b: pseudo vertical Illumination light, 14 ... stage controller, 15 ... stage, 16a, 16b ... A / D conversion unit, 17a, 17b ... storage unit, 18 ... comparison operation unit (comparison determination unit), 21 ... substrate, 22 ... insulating film (SiO ₂ films), 23a ... scratch, 23b ... thin film foreign matter, 24 ... foreign matter (particulate foreign matter), 20 ... discrimination line (threshold), 30 ... overall control unit, 31 ... storage device, 32 ... input means, 33 ... display Apparatus, 100... Defect inspection apparatus, 1 1 ... process control computer, 102 ... yield management system, 103 ... network.

Claims (25)

A stage on which the object to be inspected is placed;
An epi-illumination system that epi-illuminates illumination light composed of UV light or DUV light with a desired light beam at a position on the surface of an object to be inspected placed on the stage from a direction normal to or near the surface. And an oblique illumination system that obliquely illuminates illumination light composed of UV light or DUV light with a desired light beam at a location on the surface of the inspection object, and
Of the first reflected light generated from the spot illuminated by the epi-illumination system of the illumination optical system, the first high-angle scattered light directed at a high angle with respect to the surface of the inspection object and the illumination optical system A high-angle imaging optical system for condensing and imaging a second high-angle scattered light directed toward the high angle among the second reflected light generated from the part illuminated obliquely by the oblique illumination system, and the high A detection optical system having photoelectric conversion means for receiving the first and second high-angle scattered light imaged by the angle imaging optical system and converting the light into first and second luminance signals;
Based on the correlation between the first luminance signal and the second luminance signal converted by the photoelectric conversion means of the detection optical system, the defect on the inspection object is discriminated from a concave defect and a convex defect. A defect inspection apparatus comprising a comparison / determination unit. The defect inspection apparatus according to claim 1, wherein the epi-illumination system of the illumination optical system is configured not to generate stray light from the high-angle condensing optical system. The detection optical system further includes a light shielding unit that shields a specific light image of the first reflected light on a Fourier transform surface of the first reflected light emitted from the portion. The defect inspection apparatus according to 1 or 2. 4. The defect inspection apparatus according to claim 1, wherein the comparison / determination unit is a ratio as the correlation. The comparison / determination unit is further configured to discriminate the concave defect from a scratch and a thin film-like foreign substance based on data corresponding to the defect size calculated from the first luminance signal and the second luminance signal. The defect inspection apparatus according to any one of claims 1 to 4, wherein The comparison / determination unit is further configured to discriminate foreign matters that are convex defects based on data according to the size of the defect calculated from the first luminance signal and the second luminance signal. The defect inspection apparatus according to any one of claims 1 to 4. 5. The comparison / determination unit is configured to be able to recognize whether a discriminating convex defect is generated in a circuit pattern area or outside a circuit pattern area. The defect inspection apparatus as described in any one of these. The defect inspection apparatus according to claim 1, wherein the comparison / determination unit includes display means for displaying information on the identified defect. 8. The defect inspection apparatus according to claim 1, wherein the comparison / determination unit includes display means for displaying information on a relationship of the first luminance signal for discriminating defects. . 8. The defect inspection apparatus according to claim 1, wherein the comparison / determination unit includes display means for displaying information relating to a relationship of the second luminance signal for discriminating defects. . In the comparison and determination unit, the relationship between the first luminance signal and the second luminance signal converted by the photoelectric conversion means of the detection optical system is shown on a correlation diagram in which the horizontal axis and the vertical axis are represented by logarithmic values. The defect inspection apparatus according to claim 1, further comprising display means for plotting and displaying. The illumination optical system is characterized in that a portion on the surface of the inspection object that is incident on the epi-illumination system and a portion that is obliquely illuminated on the oblique illumination system are different in the field of view of the detection optical system. The defect inspection apparatus according to claim 1. A stage on which the object to be inspected is placed;
An epi-illumination system that epi-illuminates illumination light composed of UV light or DUV light with a desired light beam at a position on the surface of an object to be inspected placed on the stage from a direction normal to or near the surface. And an oblique illumination system that obliquely illuminates illumination light having a wavelength different from that of the illumination light composed of UV light or DUV light with a desired light beam at a location on the surface of the inspection object,
Of the first reflected light generated from the spot illuminated by the epi-illumination system of the illumination optical system, the first high-angle scattered light directed at a high angle with respect to the surface of the inspection object and the illumination optical system A condensing optical system for condensing the second high-angle scattered light directed to the high angle out of the second reflected light generated from the part illuminated obliquely by the oblique illumination system, and condensing by the condensing optical system A wavelength separation optical system for wavelength-separating the first high-angle scattered light and the second high-angle scattered light, and a first high-angle scattered light and a second high-angle scattering separated by the wavelength separation optical system. An imaging optical system that images each of the light, and each of the first high-angle scattered light and the second high-angle scattered light that is imaged by the imaging optical system and receives the first luminance signal And a detection optical system having first and second photoelectric conversion means for converting into each of the second luminance signals,
On the object to be inspected based on the relationship between the first luminance signal converted by the first photoelectric conversion means of the detection optical system and the second luminance signal converted by the second photoelectric conversion means. A defect inspection apparatus comprising a comparison / determination unit for discriminating defects. 14. The defect inspection apparatus according to claim 13, wherein the epi-illumination system of the illumination optical system is configured not to generate stray light from the high-angle condensing optical system. The detection optical system further includes a light shielding unit that shields a specific light image of the first reflected light on a Fourier transform surface of the first reflected light emitted from the portion. The defect inspection apparatus according to 13 or 14. 16. The defect inspection apparatus according to claim 13, wherein the comparison / determination unit uses a ratio as the correlation. The comparison / determination unit is further configured to discriminate the concave defect from a scratch and a thin film-like foreign substance based on data corresponding to the defect size calculated from the first luminance signal and the second luminance signal. The defect inspection apparatus according to claim 13, wherein the defect inspection apparatus is a defect inspection apparatus. The comparison / determination unit may further discriminate between large and small particulate foreign matters that are convex defects based on data corresponding to the defect size calculated from the first luminance signal and the second luminance signal. The defect inspection apparatus according to claim 13, wherein the defect inspection apparatus is configured. 17. The configuration according to claim 13, wherein the comparison / determination unit is configured to recognize whether the discriminating convex defect has occurred in the circuit pattern region or outside the circuit pattern region. The defect inspection apparatus as described in any one of these. The defect inspection apparatus according to any one of claims 13 to 19, wherein the comparison / determination unit includes display means for displaying information on the identified defect. 20. The defect inspection apparatus according to claim 13, wherein the comparison / determination unit includes display means for displaying information on a relationship of the first luminance signal for discriminating defects. . 20. The defect inspection apparatus according to claim 13, wherein the comparison / determination unit includes display means for displaying information on a relationship of a second luminance signal for discriminating defects. . In the comparison and determination unit, the relationship between the first luminance signal and the second luminance signal converted by the photoelectric conversion means of the detection optical system is shown on a correlation diagram in which the horizontal axis and the vertical axis are represented by logarithmic values. 20. The defect inspection apparatus according to claim 13, further comprising display means for plotting and displaying on the display. With respect to shallow scratches or foreign matters generated on the surface of the polished or ground film, the illumination light composed of UV light or DUV light is subjected to epi-illumination and oblique illumination with substantially the same luminous flux, and the epi-illumination and oblique illumination are performed. Scattered light generated from shallow scratches and foreign matter is received by a detector and converted into luminance signals according to the intensity of each scattered light, and shallow scratches and particulates are converted based on the correlation of these converted luminance signals. A defect inspection method characterized by discriminating foreign substances. Epi-illumination and oblique illumination of illumination light consisting of UV light or DUV light with substantially the same luminous flux is performed on a flat thin film-like foreign matter or foreign matter generated on the surface of a polished or cleaned or sputtered film. Scattered light generated from thin-film foreign matter and foreign matter by oblique illumination is received by a detector and converted into a luminance signal corresponding to the intensity of each scattered light, and based on the correlation of these converted luminance signals A defect inspection method characterized by discriminating between a thin-film foreign matter and a particulate foreign matter.

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